The use of magnetic fields for communications and the powering of short-range wireless (e.g., object detection) systems is becoming widespread in a variety of industries and technologies. Many of these systems produce large signal levels at the source (or reader) to power transducers (or tags) at short range and look for relatively small return signals from transducers. Most of these systems find application in very benign electromagnetic environments, such as, but not limited to retail outlets and filling stations.
In one type of system, the transducers may be configured as relatively simple resonators which are detected by their resonate response due to an exciting magnetic field. In a second type of system, the tag may contain transponder circuitry that is powered-up by an incident field and responds by modulating that field or generates an independent electromagnetic response. As these types of systems become more capable in range, simultaneous reading of multiple transducers, more capable transducers, etc. will be required.
Where application of such systems includes severe electromagnetic environments, such as those produced by machinery and processes (e.g., welding, induction heating, dielectric heating, industrial lighting and large electric motors) employed in heavy industry, the ability to overcome environmental interference becomes a fundamental requirement. All of these tools, when sized for heavy industry, produce significant field levels and broadband electromagnetic noise that can interfere with and even disable reader/transponder systems using magnetic fields.